Diecasting requires injection of pressurized molten metal into an assembly comprised of separable die members, each of which are constructed to withstand the internal hydraulic pressures generated by such injection when held together with sufficient force. The forces required to hold the die members together will be the resultant of the area of the casting cavity, projected on the parting plane of the die members, multiplied by the pressure of the injected metal that attempts to force the die members apart. It is this separating force that must be resisted by the locking mechanism of the casting assembly.
If two separate casting cavities or impressions are oriented side-by-side on the same parting plane of the die assembly (which is common practice for multiple casting cavities in accordance with prior art technology), and commonly injected with molten metal, the separating force will be double. These multiplying forces become unduly large when increasing numbers of castings are desired to be made in one assembly. Without modification of the diecasting assembly to reduce or withstand such forces, the advantage of higher productivity cannot be obtained.